I mean the country as a whole. The concentrations of industry in Dublin and Ulster weren’t great enough to change the national picture.
It’s true that Dublin and Ulster were the most strongly Unionist parts of Ireland. I think relative economic prosperity accounts for part of this, but only part. Dublin wasn’t actually that prosperous; it was a massively socially stratified city, with a comfortable middle class bolstered by government employment, but at the bottom was a very large underclass who lived in considerable poverty. 25% of the population lived in slum accommodation where there was one room or less per family; there was no city in Britain of which that could be said.
Ulster was more genuinely prosperous but, honestly, I think support for the Union had less to do with that and more to do with the sectarian politics of the province. (Which was also a factor in Dublin, but to a lesser extent.)
Apart from Dublin, the places in Ireland which did best, economically, out of the Union were the garrison towns. But they were mostly strongly Nationalist in sentiment.
As long as Scottish independence is not a done deal, the EU will do nothing which could be construed as encouraging, facilitating or presuming the likelihood of Scottish independence. But once it’s agreed and acknowledged within the UK that Scotland is going to become independent - a new referendum vote for independence, Westminster acknowledges the result and commits to implementing it, a transition to independence begins - I think the picture changes. EU talks about accommodating Scotland make complete sense, and I think could begin without any suggestion that the EU is thereby involving itself in bringing about the breakup of the UK. Rajoy doesn’t draw attention to this because, well, we know why, but I think it’s the reality.
I take your point that, no matter how early talks with the EU begin and how favourably they work out, Scotland leaving the UK is an economically challenging transition.